President Barack Obama on Thursday authorized night airstrikes to protect U.S. personnel in Iraq and prevent the "genocide" of religious minorities under siege from brutal Islamic militants who've been rampaging through northern Iraq.

Obama added that humanitarian airdrops to the trapped and starving minorities already began Thursday.

"When we have the unique capabilities to help avert a massacre, then I believe the United States of America cannot turn a blind eye," the president said in a somber news conference.

"Today, America is coming to help."

Obama suggested no airstrikes had yet begun, and said the "targeted strikes" will be launched should the extremist Islamic State of Iraq and Syria, also known as ISIS or the Islamic State "move toward [Irbil], if they threaten our personnel" in either Irbil or Baghdad.

"The United States cannot and should not" intervene every time there's a crisis, he said, adding, however, "we face a situation … when innocent people face violence on a horrific scale… and we can act … to prevent genocide."

Still, Obama emphasized, "American combat troops will not be returning to fight in Iraq."

A senior U.S. defense official told NBC News that "a number of U.S. military aircraft" had already successfully delivered food and water and had "safely exited the immediate airspace" without a shot having been fired.

A U.S. official told The Wall Street Journal some 70 pallets of water and meals-ready-to-eat were dropped into the mountains were the Kurdish religious minority Yazidis were stranded.

Pentagon officials watched video the airdrops, conducted by both C-17 and C-130 cargo planes, recorded from an overhead surveillance plane, the Journal reported, adding officials said the cargo planes were escorted by American fighter jets.

Vian Dakhil, the only Yazidi in the Iraqi parliament, earlier this week accused the Islamic State of genocide against the Yazidi populations, declaring, "There is a collective attempt to exterminate the Yazidi people," the Journal reported.

The White House said Vice President Joe Biden called Masoud Barzani, the regional president in Iraqi Kurdistan, to reaffirm the president was committed to take "whatever actions necessary to protect Americans in Irbil, including targeted airstrikes."

Obama's announcements marked the deepest American engagement in Iraq since U.S. troops withdrew in late 2011 after nearly a decade of war.

Earlier Thursday, an Iraqi military official told The Wall Street Journal the Iraqi air force conducted strikes Thursday in Nineveh on the city of Mosul and closer to Irbil province, and on Tikrit in Salaheddine province. The air force has bombed insurgent positions in Mosul and in Tikrit — which Islamic State took on June 11, the day after it seized Mosul — and its surroundings as part of a counteroffensive, Iraqi officials say.

The Journal reported Islamic State insurgents took over six towns in northern Iraq over the past two days — two of them after the Kurdish regional forces guarding them, the Peshmerga, withdrew.

The 190,000-strong Peshmerga are well-trained but not well-equipped, the Journal reports.

"People are fleeing because there is no trust that the Peshmerga can protect them," Yonadam Kanna, a parliamentarian and the leader of the Assyrian Democratic Movement, one of the strongest Christian parties in Iraq, told the Journal.

"This isn't an equal fight between the Peshmerga and the Islamic State. The Islamic State has much bigger and more powerful weapons than the Peshmerga do. These people want to die and have lunch with the Prophet Muhammad. The Peshmerga want to live and go home to have dinner with their wives. They won't play as dirty as the Islamic State does in war."

Obama's final decision came on a proposal that had been on the table all day, a top Iraqi diplomat told CNN.

"There is some communication between Baghdad and Washington on that issue, but no strike has been done yet," said Mohammad Ali Al-Hakim, Iraq's Ambassador to the United Nations.

Republican Sens. John McCain of Arizona and Lindsey Graham of South Carolina, who are both on the Senate Armed Services Committee, criticized the aid and targeted strikes as "far from sufficient to meet the growing threat that ISIS poses," and warning "expansionist" insurgents "must be stopped."

"If ever there were a time to reevaluate our disastrous policy in the Middle East, this is it," they said. "Because of the president's hands-off approach, the threats in the region have grown and now directly threaten the United States. ... and if we do not change course, the costs of our inaction will only grow."

Before the president's announcement, The New York Times had reported an announcement on Kurdish television of what was described as a U.S. intervention triggered street celebrations and horn-honking in town under siege by ISIS.

The strike will be protective of not only the stranded refugees forced by the Islamic State from their homes, but a U.S. diplomatic consulate in Irbil, as well as a military operations center there that is advising and assisting the Iraqi military in that region.

The fast-moving developments unfolded as the Islamic State militants stormed through villages in the north of Iraq, home to religious minorities including Christians and the Yazidis, who follow an ancient religion with ties to Zoroastrianism.

The extremists also seized Iraq's largest dam Thursday, placing them in control of enormous power and water resources and access to the river that runs through the heart of Baghdad.

"The situation is nearing a humanitarian catastrophe," White House spokesman Josh Earnest said earlier Thursday. "We are gravely concerned for their health and safety."

Earnest singled out the plight of the Yazidis. Thousands fled their homes after the Islamic State group issued an ultimatum to convert to Islam, pay a religious fine, flee their homes, or face death. Many of the Yazidis now are trapped on a mountain without food or water.

They are in desperate need of help, CNN reported. Other groups targeted by the hard-line Islamic State include Shiite Muslim, Turkmen, and Shabak, all of them religious minorities.

The United Nations estimates 200,000 people heading toward Kurdistan in the past 48 hours, CNN reported.

And outside Irbil, the refugees were sleeping in parking lots or shells of buildings under construction with little access to water or any other services, CNN's Ivan Watson reported.

Also Thursday, Pope Francis pleaded with the international community to take steps to help the thousands of Christians who fled their homes on Wednesday night after the latest onslaught from the Islamic State, the Catholic News Service reported.

The Vatican issued a statement saying that the pope is making a "pressing appeal to the international community to take initiatives to put an end to the humanitarian drama underway, to take steps to protect those involved and threatened by violence and to ensure the necessary aid for so many displaced people whose fate depends on the solidarity of others."

The ISIS has been on an unrelenting land grab in northern Iraq, including the city of Mosul, over the past two months.

They're also waging campaigns for territory in Syria and Lebanon in their quest to create a unified Islamic state encompassing territory from all three countries.

The Iraqi government has asked for military assistance from the United States – and up until Thursday, Obama has resisted, saying any military might is contingent on Iraq reforming its political system to be more inclusive – something the United States hopes will quell the roiling sectarian tensions there.

Obama reaffirmed there'd be no "boots on the ground" during the airstrikes, and emphasized "Iraq needs to come together to doge a new government," and that the United States "will work with our friends and allies and help Iraqis push back against" the Islamic State terror.

"There are no American military solutions to the problems in Iraq," Earnest said earlier Thursday.

The United States has already sent more than 800 U.S. forces to Iraq this year following the Islamic State's gains. More than half are providing security for the embassy and U.S. personnel.

American service members also are involved in improving U.S. intelligence, providing security cooperation and conducting assessments of Iraqi capabilities.

If the president were to approve imminent airstrikes in Iraq, it's likely to be without formal congressional approval; lawmakers left town last week for a five-week recess.

The administration, along with the United Nations, is facing increasing pressure to get more involved to prevent the crisis from worsening, Fox News reported.

"Genocide is taking place before our eyes — and on your watch — in Iraq," Rep. Frank Wolf, R-Va., wrote in a letter earlier this week to Obama.

France on Thursday called for an urgent U.N. Security Council meeting on the crisis.

President Barack Obama Thursday night authorized airstrikes to protect U.S. personnel in Iraq and prevent the "genocide" of religious minorities under siege from brutal Islamic militants who've been rampaging through northern Iraq.